共查询到17条相似文献,搜索用时 140 毫秒
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采用蒙特卡罗程序MCNP/4B模拟计算了功率为30kW的低浓化医院中子照射器的堆芯物理参数,设计了合理的堆芯布置方案、235U富集度、控制棒价值、后备反应性和停堆深度,得到固有安全性较高、寿期达10年且无需换料、采用低浓化UO2燃料的医院中子照射器的堆芯物理设计方案,为后续反应堆工程设计以及硼中子俘获治疗肿瘤用中子束的设计提供理论依据。 相似文献
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医院中子照射器装置于2007年开始建造,2008年12月完成了反应堆厂房建造,2009年3月完成了相关系统的安装和调试。2009年12月7日首次达到临界,2010年1月22日达到满功率运行。物理调试结果表明,医院中子照射器反应堆最终后备反应性为4.2 mk,满功率最大可连续运行时间为12 h,功率波动小于0.3%;4.2 mk反应性释放实验表明,反应堆在229 s时达到85.7 kW的最大峰值功率,随后,由于燃料元件多普勒效应和慢化剂的负温度效应会非能动地把功率限制在允许的安全水平之下,反应堆具有良好的固有安全特性。 相似文献
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迈入新世纪的硼中子俘获疗法(BNCT) 总被引:1,自引:0,他引:1
扼要叙述进入21世纪之际,硼中子俘获疗法(boron neutorn capture therapy,BNCT)在国际范围内的一些显著进展,包括BNCT的临床定位、肿瘤复发的探索、硼浓度的定量探测、靶向掺硼药物的开发以及我国医院中子照射器的问世.这些BNCT长期开发中的瓶颈趋于缓解,预示了BNCT个性化与例行化的前景更为清晰. 相似文献
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作为中国核工程开发海外市场的旗舰,中原对外工程有限公司将项目开发作为发展引擎,在百万千瓦级核电项目开发、研究性核反应堆项目开发、多功能医院中子照射器开发研究及多用途模块式小型反应堆项目开发工作中不懈努力,为和平利用核能、核技术做出贡献. 相似文献
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A significant nuclear-physical feature of boron-containing systems, distinguishing them from all other, except fluoride, systems,
is considerable flux of fast neutrons generated by the (α,n) reaction on boron nuclei. The neutron flux generated on boron nuclei is higher by approximately an order of magnitude than
that excited on nuclei of other components of the borobasalt matrix. The calculated and measured neutron flux values are well
consistent. The neutron generation is mainly determined by the reaction of α-particles with O, Si, and Al nuclei and is thus
characteristic of any aluminosilicate system. 相似文献
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A.I. Ioffe 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1984,228(1):141-146
The operation of neutron interferometers is analyzed with particular emphasis on the Moiré effects present. The high sensitivity of neutron interferometers to deflection of the incident and propagating beams is shown to make these instruments a promising tool in the experimental search for an electric charge on the neutron. The corresponding estimates for interferometers of different types are given.It is shown that by using diffraction grating interferometers for very cold neutrons, the present-day upper limit for the neutron charge can be lowered by several orders of magnitude. 相似文献
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Ogata T Kudo S Watanabe Y Muramatsu T Yamamoto H Iwai S Takagi S Harano H Matsumoto T Nishiyama J 《Radiation protection dosimetry》2011,146(1-3):107-110
Bonner sphere spectrometer (BSS) is used in radiation protection measurement because of its wide energy range (thermal to MeV) and easy operation. Mitsubishi Heavy Industries (MHI) has used BSS to obtain neutron spectrum and has used the neutron spectrum to estimate neutron dose or induced activity. Calibration of BSS is important to estimate precise neutron dose or induced activity. MHI BSS was calibrated at National Institute of Advanced Industrial Science and Technology (AIST). The calibration results at AIST are in good agreement with calculation results. 相似文献
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O. Kirichek T. J. Foster R. B. E. Down D. Clapton C. R. Chapman J. Garside Z. A. Bowden 《Journal of Low Temperature Physics》2013,171(5-6):737-744
Today almost a quarter of all neutron scattering experiments performed at neutron scattering facilities require sample temperatures below 2 K. However, a global shortage of helium gas can seriously jeopardise low temperature experimental programmes at neutron scattering laboratories. Luckily the progress in cryo-cooler technology offers a new generation of cryogenic systems with significantly reduced consumption and in some cases nearly a complete elimination of cryogens. Here we discuss design and test results of a new cryogen free top-loading cryostat developed through an ISIS and Oxford Instruments collaborative project. The cryostat provides neutron scattering sample environment in the temperature range 1.4–300 K. High cooling power (0.23 W at temperature less than 2 K) achieved at the cryostat’s variable temperature insert heat exchanger allows operation of a standard dilution refrigerator insert in a continuous regime. From a user perspective, the system offers operating parameters very similar to those of an Orange cryostat but without the complication of cryogens. 相似文献
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Cihangir Çelik Kenan ÜnlüVijaykrishnan Narayanan Mary J. Irwin 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,652(1):370-373
Soft errors are transient errors caused due to excess charge carriers induced primarily by external radiations in the semiconductor devices. Soft error phenomena could be used to detect thermal neutrons with a neutron monitoring/detection system by enhancing soft error occurrences in the memory devices. This way, one can convert all semiconductor memory devices into neutron detection systems. Such a device is being developed at The Pennsylvania State University and named Neutron Intercepting Silicon Chip (NISC). The NISC is envisioning a miniature, power efficient, and active/passive operation neutron sensor/detector system. NISC aims to achieve this goal by introducing 10B-enriched Borophosphosilicate Glass (BPSG) insulation layers in the semiconductor memories. In order to model and analyze the NISC, an analysis tool using Geant4 as the transport and tracking engine is developed for the simulation of the charged particle interactions in the semiconductor memory model, named NISC Soft Error Analysis Tool (NISCSAT). A simple model with 10B-enriched layer on top of the lumped silicon region is developed in order to represent the semiconductor memory node. Soft error probability calculations were performed via the NISCSAT with both single node and array configurations to investigate device scaling by using different node dimensions in the model. Mono-energetic, mono-directional thermal and fast neutrons are used as the neutron sources. Soft error contribution due to the BPSG layer is also investigated with different 10B contents and the results are presented in this paper. 相似文献
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Fernández F Amgarou K Domingo C García MJ Quincoces G Martí-Climent JM Méndez R Barquero R 《Radiation protection dosimetry》2007,126(1-4):371-375
Positron emission tomography (PET) is a non-invasive medical imaging technique normally used for diagnostic purposes to determine the location and concentration of physiologically active compounds in a human body. An unshielded cyclotron is used for PET at the Clinica Universitaria de Navarra to produce short-lived positron emitting radionuclides ((15)O, (13)N, (11)C and (18)F) by bombarding appropriate target material with proton or deuteron beams with energies up to 18 and 9 MeV, respectively. Subsequent nuclear reactions may generate undesirable neutrons that should be evaluated and controlled. In this study, the neutron measurements performed with an active and a passive Bonner sphere systems at different locations outside and inside the cyclotron vault during operation have been presented. The neutron spectrum at each location was determined with an unfolding code developed by the authors. 相似文献
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S.M. Robinson R.C. RunkleR.J. Newby 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,652(1):404-407
Direct detection of fast neutrons using organic scintillators is one alternative to moderated thermal neutron detectors deployed to detect fission neutrons—a relevant question in light of dwindling 3He supplies. Recent developments in materials science have demonstrated the capability to grow larger crystals in reasonable times. In light of these developments, this study compares the relative performance of a 3He-based neutron module from a commercially available portal monitor with a theoretical organic scintillator of similar overall size. Stilbene serves as a benchmark with its performance estimated from a combination of energy deposition modeled by radiation transport calculations and an assumption of the lowest neutron energy at which pulse shape discrimination can effectively separate neutron and gamma-ray events. Before intrinsic detection efficiencies on par with moderated detector systems can be achieved, the results point to the need for further advances including significant increases in detector size, especially thickness, and/or lower pulse shape discrimination thresholds. 相似文献